Cooling of components such as gas turbine blades has been done by routing cooling air through channels in the component; passing the coolant through pores in the outer walls for film cooling; passing the coolant along interior surfaces of the walls for near-wall cooling; and/or directing jets of the cooling air against the walls for impingement cooling.
In addition, porous constructions have been formed on component walls to thermally couple the coolant to the wall. Methods of manufacturing porous constructions for this purpose have included casting, selective metal sintering or melting (SLS, SLM), and others. The porous element may be formed separately and then bonded to the structural wall, or a porous element may be formed integrally with a wall in a single process. Examples of prior methods are found in U.S. Pat. No. 7,670,675.
Prior methods did not provide different materials for the porous cooling elements and the structural elements of a component. This constrained optimization of a porous element for its intended cooling function if materials optimized for a high-temperature structural wall are also used for the porous element. However, bonding different materials is challenged by differential thermal expansion when the bond is exposed to large temperature variations as in a gas turbine.